Race-free eGFR equation attenuates racial disparities in accrual of preemptive wait time
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In a theoretical context, the 2021 creatine-based Chronic Kidney Disease Epidemiology Collaboration equation reduced racial differences in preemptive wait time accrual more than the use of the creatinine-cystatin equation, this study shows.
Therefore, the race-free creatinine-based eGFR equation may reduce racial differences to preemptive wait time accrual, researchers wrote.
As Healio previously reported, Elaine Ku, MD, MAS, of the University of California, San Francisco, and colleagues found the inclusion of race in eGFR equations led to a shorter time to kidney failure for Black patients. This study revealed a similar time to kidney failure between Black and white patients when using the new race-free equation.
Study
In this retrospective cohort study, Ku and colleagues evaluated data of Black and white patients from the Chronic Renal Insufficiency Cohort (CRIC) study to determine if using the 2021 Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations for measuring eGFR and eligibility for preemptive waitlisting would correlate with racial differences to wait time accrual.
Two theoretical cohorts were created of patients who were potentially eligible for preemptive wait time accrual using either the 2021 CKD-EPI creatinine equation or the 2021 CKD-EPI combined creatinine-cystatin C equation to measure GFR.
All patients reported at least one eGFR of less than 25 mL/min per 1.73 m2 and a subsequent eGFR of at least 20 mL/min per 1.73 m2 during their participation in the CRIC study using the 2021 CKD-EPI equations.
Researchers conducted Weibull accelerated failure time and cause-specific hazard models to identify the relationship between race and time to kidney failure from the qualifying visit when a patient’s eGFR fell to at least 20 mL/min per 1.73 m2. Additionally, researchers used the 2021 creatinine- or creatinine cystatin C-based equation through a bootstrapping approach to assess differences in time ratios from models.
Results
Overall, 472 patients were eligible for waitlist registration when using the creatinine equation, and the potential preemptive wait time was similar for both Black and white patients. In contrast, 441 patients were eligible for waitlist registration when using the creatinine-cystatin C equation, and potential wait time was 20% shorter for Black patients than white patients.
When using the creatinine equation, the median wait time that could be accrued for Black patients was 23 months vs. 22 months in white patients; whereas the median wait time that could be accrued for Black patients vs. white patients when using the creatinine-cystatin C equation was 21 months and 26 months, respectively.
Bootstrapping revealed a significant difference in the ratio of time ratio of models using the creatinine vs. creatinine-cystatin C equation.
“We believe that the findings in our study are helpful in providing some preliminary data on how use of the different GFR estimating equations would theoretically affect wait time accrual prior to the start of dialysis,” Ku said in the press release. “We found that the new creatinine-based equation seemed to be associated with more similar wait time that could potentially be accrued compared with use of the cystatin-C based equation, but our findings require further validation in larger groups of patients.”
In an accompanying editorial, Rhiannon D. Reed, MPH, DrPH, assistant professor at Heersink School of Medicine, and Jayme E. Locke, MD, MPH, FACS, FAST, a transplant surgeon and the director of the division of transplantation surgery at the University of Alabama at Birmingham and the director of the Comprehensive Transplant Institute at the university, wrote, “We commend the authors for this well-designed study that promotes future work to explore the cost and policy implications of the broad availability of cystatin C and genetic ancestry testing; the need for data on the implications of the race-free equation in other areas of clinical decision-making on the basis of kidney function; and further refinement of formulas that utilize existing clinical measurements, minimize bias and maximize accuracy.”
Reference:
- How might eliminating race-based adjustments in estimates of kidney function affect kidney transplant waitlisting? https://www.newswise.com/articles/how-might-eliminating-race-based-adjustments-in-estimates-of-kidney-function-affect-kidney-transplant-waitlisting?sc=mwhr&xy=10007438. Published Sept. 19, 2022. Accessed Sept. 19, 2022.
- Reducing racial disparities in access to transplant in the United States one step at a time. https://cjasn.asnjournals.org/content/early/2022/09/19/CJN.09590822.Published Sept. 19, 2022. Accessed Sept. 19, 2022.
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